The Eye Care Advocate

Charles Bonnet Syndrome: A Guide for Eye Care Professionals

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by

Jason Searle
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This article about Charles Bonnet Syndrome is intended for a professional audience, including eye care and medical professionals, for educational purposes. It does not constitute bespoke medical advice. Should you or a person you care for experience hallucinations or any significant changes to their vision, please seek urgent advice from an eye care professional.

What is “Charles Bonnet Syndrome” I hear you ask? Charles Bonnet Syndrome is a condition that causes people with sight loss to see things that are not really there1,2. These are vivid, silent, visual hallucinations2,3,4. It is crucial for us as clinicians to understand that this is not a mental health problem or dementia3; it is a direct and surprisingly common consequence of losing your vision2.

My first real encounter with Charles Bonnet Syndrome was long before I was an optometrist, back when I worked as an OCT technician in a busy eye hospital. I bonded with a wonderful lady who I saw every few weeks for her macular degeneration. She suffered terribly with her hallucinations. When she was stressed, she would see floating horses’ heads in the sky; her reflection in the television would snarl and twist into a grotesque, gargoyle-like face and, on occasion, she would suddenly see her front room burst into flames. At the time, all I could do was listen.

“…and, on occasion, she would suddenly see her front room burst into flames.”

Jason Searle, talking about a patient he encountered that described her Charles Bonnet Syndrome hallucinations.

Her story highlights the reality of this condition, which happens because the brain starts to ‘fill in the gaps’. When the eyes stop sending as much visual information as they used to, the brain doesn’t just quieten down. Instead, it can become hyperactive and generate its own images from its vast library of memories and imagination. This is why some patients see simple patterns3, while others see fully-formed people, animals, and landscapes2,3.

a decorative image of a watercolour painting, showing a very scared elderly lady with white hair and purple top on the right of the image and on the left the sky is filled with severed horses heads and below them is a cottage on fire. This decorative image is to illustrate the experience tha Jason's patient had with Charles Bonnet Syndrome

Who Was Charles Bonnet?

It’s natural to wonder where the name for this condition comes from. Charles Bonnet was an influential Swiss naturalist and philosopher1,2 who lived in the 18th century (1720-1793). Though a lawyer by trade, his passion was science. In 17602, he provided the first detailed description of the syndrome when documenting the experiences of his 87-year-old grandfather, Charles Lullin.

Lullin was a man of sound mind but was nearly blind from severe cataracts2. He described seeing vivid, detailed images of people, birds, buildings, and elaborate tapestries that he knew were not real. Bonnet’s meticulous documentation was crucial because he recognised that these hallucinations were not a sign of madness, but rather a direct result of his grandfather’s failing vision. Interestingly, later in life, as Bonnet’s own eyesight deteriorated, he too began to experience the very same symptoms. It wasn’t until 1937 that the condition was formally named Charles Bonnet Syndrome in his honour by the neurologist Georges de Morsier1.

A decorative image illustrating Charles Bonnet Syndrome described by his grandfather. The scene is a watercolour with large, dark purple birds in the centre. Surrounding them is a tapestry of buildings and plants.

How Common is Charles Bonnet Syndrome?

The prevalence is shockingly high. Research suggests that at least one in five people with significant sight loss experience Charles Bonnet Syndrome, with some studies indicating rates as high as 60%6 in those with severe impairment. It is thought that these figures are under-reported2.

This means there could be over a million people in the UK living with the condition right now. Yet it’s often a topic relegated to a footnote. This article is a call to all of us in the eye care profession to bring Charles Bonnet Syndrome out of the shadows. “Why?” I hear you ask. Simply put, many patients are scared to report their symptoms and are suffering in silence.

Why do Patients Avoid Reporting the Hallucinations?

The single biggest barrier to helping patients with Charles Bonnet Syndrome is their fear. They don’t speak about it because they are terrified of being dismissed as “senile” or “losing their marbles.” They worry that these visual hallucinations are a sign of a severe mental health decline, such as dementia or psychosis2,4. The reality, of course, is that Charles Bonnet Syndrome is a recognised condition directly linked to their sight loss.

The things patients see can be varied. Some may only report seeing geometric shapes floating around them. Others may be like my patient mentioned above – seeing faces, or even people. The latter may be harder to explain to a relative or a healthcare professional – for the fear of ridicule or diagnosis of cognitive decline2.

Decorative image shows a man with white hair and beard looking worried about disclosing his Charles Bonnet Syndrome symptoms. A Thought bubble emerges into the right side of the image saying ""Who will believe me". It is in hues of purple and watercolour style.

The Power of Asking: Suspecting Charles Bonnet Syndrome

As clinicians, we cannot wait for patients to bring up these symptoms. Most never will. We have to take the lead and create a safe space for them to share. Over the years, I’ve developed a way to gently open the door to this conversation with any patient who has significant vision loss. I’ll say something like: “I have a strange question for you, but do you sometimes see things that you don’t think are really there? Things like shapes, lights, people, or animals?”

The reaction is often immediate and profound. It’s as if a huge weight has been lifted from their shoulders. The relief on their face is palpable as they realise they aren’t the only one, that they aren’t “going mad.”

“The relief on their face is palpable”

Jason Searle, The Eye Care Advocate

I then follow up by explaining what Charles Bonnet Syndrome is in simple terms: “Sometimes, when people lose a lot of their sight, the brain likes to guess what it’s missing from the input of your eyes, and it often gets it wrong.“ Simply giving their experience a name, a diagnosis, is incredibly powerful. It validates their reality, removes the stigma, and is the first and most critical step in helping them manage their Charles Bonnet Syndrome.

A Tale from My Clinic

I remember seeing a 96-year-old lady as we emerged from the lockdowns. She had been booked in for a flashes and floaters appointment by the reception team. Upon discussing the symptoms, and being aware she was only seeing 1/60 in her “good eye”, I asked for a better description of the “flashes and floaters” she had reported.

“They are like blue, neon snowflakes that dance around in front of me, with neon-green leaves that then climb up the wall“, she explained. Her daughter, present, had said she was worried it was the start of dementia and had a GP appointment booked soon.

I then explained about Charles Bonnet Syndrome. I asked if she had ever seen other “things” that she thought were not actually there. What she told me still shocks me today.

“Yes, actually. Last night I awoke and saw a man with a disfigured face floating above my bed. He was grinning sinisterly at me. I told him to go away, batted my hands at him and then he vanished. I then went down to pour myself a brandy and went back to bed.“

Her daughter was horrified as she had not been told this. Apparently these experiences had been going on for years; starting not long after her wet macular degeneration had been diagnosed.

I then explained the condition, how it presents and what causes it. My patient was in tears – tears of relief, I may add – as she had been terrified of being told she was “going mad” or “losing her mind”. Her daughter, now armed with this information was better equipped to discuss the problems with her GP.

An illustration of the hallucination that one of Jason's patients had with Charles Bonnet Syndrome. The left of the image is a grotesque man with a horrifying face and glowing green. Surrounding hem are blue snowflakes and green, climbing vines with dendrite ends to them. To the right is an elderly lady in her bed looking concerned, whilst looking at the man.

Supporting Patients with Esme’s Umbrella

Once you have suspected that Charles Bonnet Syndrome is present, your next step should be to connect the patient with specialist support. This is where the charity Esme’s Umbrella becomes an absolutely vital resource.

Their work in raising awareness is crucial to preventing people from suffering in silence. They get patients, families, and clinicians talking about Charles Bonnet Syndrome. They fund and facilitate essential research into why it happens and how we can find ways to manage or even remove the symptoms.

In a world where research funding is often directed towards more common, clinically treatable conditions, the work of advocacy groups like Esme’s Umbrella is indispensable.

You can visit by clicking the link below: but if you do wish to share this website with your patients or your team the website address is:

https://www.charlesbonnetsyndrome.uk

You can also call the Helpline – Esme’s Umbrella at the RNIB via the number below (please note, calls will be answered by the RNIB, who are answering calls in conjunction with Esme’s Umbrella)

0303 123 9999

I now signpost all my patients with Charles Bonnet Syndrome to them. The change in these patients at their follow-up appointments is noticeable. Armed with information, coping strategies, and the knowledge that there is a community of support, they are more confident and open about their experiences.

Esme’s Umbrella provides the answers and reassurance that we, in a busy clinic, can’t always fully provide. It is our duty to ensure our patients know about them.

Our Professional Responsibility with Charles Bonnet Syndrome

So, what is our duty of care as eye care professionals when it comes to Charles Bonnet Syndrome? It is more than just knowing the definition. Our responsibility is to be proactive. The single most important message I want every optometrist and ophthalmologist to take away from this is that we have to ask the question. We must integrate screening for Charles Bonnet Syndrome into our routine care for every patient with low vision2.

Beyond that, we need to be prepared. We need to know some basic management tips to offer patients and we absolutely must know where to signpost them to for further help, with Esme’s Umbrella being the primary resource. We should also communicate our findings to the patient’s GP.

“Our responsibility is to be proactive!”

Jason Searle, The Eye Care Advocate

This ensures they are aware of the diagnosis of Charles Bonnet Syndrome, and ensures the patient’s wider healthcare team understands that their hallucinations are linked to their vision loss. This is a fundamental part of our duty of care.

The GP may then wish to perform other cognitive and neurological tests to confirm the diagnosis and rule out other causes of hallucinations. As there are some “culprit” medications5 that have been found to trigger or exacerbate the hallucinations, the doctor may be able to review these medications and prescribe alternatives in appropriate cases.

A decorative image of a doctor comforting a worried patient.

Practical Coping Strategies for Charles Bonnet Syndrome

Beyond providing a diagnosis and reassurance, we can offer practical advice to help patients manage their hallucinations. These strategies, often promoted by Esme’s Umbrella and based on clinical observation, can empower patients to feel more in control. It’s important to explain that what works for one person may not work for another, but having a toolkit of options is invaluable.

Here are some key coping mechanisms to discuss with your patients:

  • Change the Lighting3,5
    Hallucinations are often worse in dim, monotonous light. Advise the patient to turn on a brighter light or, conversely, if in bright light, to move to a dimmer area.
  • Move and Interact3,5
    Simply getting up and moving to a different room can sometimes dispel an image. Encourage them to interact with the hallucination – reach out to touch it or blink rapidly.
  • Eye Movements3,5
    Based on the work of Dr. Dominic ffytche, a leading expert in Charles Bonnet Syndrome, a specific exercise can help. Advise the patient to keep their head still and move their eyes from left to right about once a second for 15-30 seconds. This may need to be repeated a few times.
  • Increase Sensory Input3,5
    The brain is trying to fill a sensory void. Doing something else that engages the brain, like turning on the radio, listening to music, or starting a conversation, can help push the hallucinations away.
  • Acknowledge and Dismiss3,5
    Remind them that they are in control. Sometimes, confidently staring directly at the image and telling it to “go away” can be effective.

More tips and strategies can be found on the Esme’s Umbrella website.

Conclusion

Charles Bonnet Syndrome is a condition that lives in the shadows, fueled by fear and misunderstanding. As eye care professionals, we hold the key to bringing it into the light. By asking a simple question, we can transform a patient’s experience from one of secret terror to one of validated understanding. This can empower the patient4 and make a huge difference to their quality of life.

We can replace fear with knowledge and isolation with community. This is about more than just a diagnosis; it’s about restoring a patient’s peace of mind. The toolset provided above can also be shared with patients and provide them a way to help manage their hallucinations. We have the power to make that difference, but only if we ask.

A decorative watercolour image showing a landscape with purple clouds flowing through the top of the image. Within the clouds are gargoyles with scary faces. A lone elderly lady wanders into the scene on a brown path. She is wearing purple and carrying a bright orange umbrella - in reference to Esme's Umbrella - the charity involved in providing support and research into Charles Bonnet syndrome.

Frequently Asked Questions

What are the definitive diagnostic criteria for Charles Bonnet Syndrome?

The core criteria are visual hallucinations in a patient with acquired vision loss, with the patient having insight that the hallucinations aren’t real, and in the absence of any other neurological or psychiatric condition that could explain them.

What’s the best way to open a conversation about potential hallucinations?

Use a gentle, normalising question like, “Some people with sight loss find they see things that aren’t really there, like patterns or shapes. Has anything like that ever happened to you?” This approach removes stigma and opens the door for the patient to share.

Are there any proven pharmacological treatments for Charles Bonnet Syndrome?

Currently, there is no single licensed or universally effective medication for CBS4. While some drugs used for epilepsy or anxiety have been tried in severe cases, the primary management focuses on reassurance, education, and coping strategies4.

What is the typical prevalence rate I should expect in my low vision clinic?

The prevalence is high but often under-reported; expect that at least 1 in 5 of your patients with significant sight loss may have Charles Bonnet Syndrome, with some studies suggesting this could be much higher.

How should I document a diagnosis of Charles Bonnet Syndrome in the patient’s record?

Clearly state the diagnosis of “Charles Bonnet Syndrome,” describe the nature of the patient’s hallucinations, and note the advice and resources (like Esme’s Umbrella) that you have provided. It’s also vital to record their visual acuity at the time.

What’s the correct way to communicate a Charles Bonnet Syndrome suspect to the patient’s GP?

Write a clear letter to the GP stating your tentative diagnosis and that it is a direct consequence of the patient’s sight loss, and not likely a mental health condition. This helps prevent misdiagnosis and ensures the whole healthcare team is informed. The GP may wish to perform additional cognitive tests to rule out other conditions and confirm a diagnosis of Charles Bonnet Syndrome.

Are there any known triggers that can make the hallucinations worse?

Yes, common triggers for Charles Bonnet Syndrome hallucinations include stress, fatigue, social isolation2, and periods of inactivity or low sensory input2, such as sitting alone in a quiet, dimly lit room.

How do I reassure a patient who is terrified by their hallucinations?

The most powerful tool is education. Clearly explain that Charles Bonnet Syndrome is a known, common side effect of sight loss and not a sign of mental illness, and reassure them that they are not alone in this experience.

Can children with congenital or acquired sight loss experience Charles Bonnet Syndrome?

Yes, although it is less commonly reported, children and young adults with sight loss can and do experience Charles Bonnet Syndrome. It’s crucial to ask the question in paediatric low vision clinics as well.

If a patient has both hearing loss and vision loss, can hallucinations be auditory too?

True Charles Bonnet Syndrome involves only visual hallucinations. If a patient is also experiencing auditory or other sensory hallucinations, this would warrant further investigation by their GP to rule out other causes.

References and Further Reading on Charles Bonnet Syndrome

  1. De Morsier G (1967). The Charles Bonnet Syndrome: visual hallucinations of the aged, without mental deficiency. Annales Médico-Psychologiques 2(5), 677–702.
  2. Rojas LC, and Gurnani B (2023). Charles Bonnet Syndrome. StatPearls [Online]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK585133/ [Accessed on: June 16th 2025].
  3. NHS (2022). Charles Bonnet Syndrome. NHS Website [Online.] Available at: https://www.nhs.uk/conditions/charles-bonnet-syndrome/ [Accessed: 16th June 2025].
  4. Best J, Liu PY, Ffytche D, Potts J, and Moosajee M (2019). Think sight loss, think Charles Bonnet syndrome. Thereapeutic Advances in Ophthalmology 11: 1-2.
  5. Esme’s Umbrella (no date). Managing CBS. Esme’s Umbrella [Online]. Available at: https://www.charlesbonnetsyndrome.uk/managing-cbs [Accessed: 16th June 2025].
  6. ffytche DH (2009). Visual hallucinations in eye disease. Current Opinions in Neurology 22: 28–35.

Please also check out the following resources that help provide support for those with Charles Bonnet syndrome:

Please note, the list above is not exhaustive and I welcome other suggestions of resources and support groups that may exist for those with Charles Bonnet Syndrome. Further links, specific to different eye diseases that may be associated with Charles Bonnet Syndrome may be found on the links pages.

If you are an eye care professional that wishes to improve their general case history-taking skills, my book “History and Symptoms: The Eye Examination” is currently available to buy on Amazon. All purchases help to cover the costs of running this website, whilst the skills you can learn will help to boost your communication skills.

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